During the drilling and completion of oil and gas wells, it may be necessary to engage in ancillary operations, such as evaluating the production capabilities of formations intersected by the wellbore. For example, after a well or well interval has been drilled, zones of interest are often tested to determine various formation properties such as permeability, fluid type, fluid quality, fluid density, formation temperature, formation pressure, bubble point, formation pressure gradient, mobility, filtrate viscosity, spherical mobility, coupled compressibility porosity, skin damage (which is an indication of how the mud filtrate has changed the permeability near the wellbore), and anisotropy (which is the ratio of the vertical and horizontal permeabilities). These tests are performed in order to determine whether commercial exploitation of the intersected formations is viable and how to optimize production.
Tools for evaluating or surveying formations and fluids in a well bore may take a variety of forms, and the tools may be deployed downhole in a variety of ways. For example, the evaluation tool may include a formation tester having an extendable sampling device, or probe, and pressure sensors. The evaluation tool may include a fluid identification (ID) system with sampling chambers or bottles. Sensor instrumentation, including orientation responsive sensors such as a magnetometers or accelerometers, can be used to survey the formation and create a profile, model, or image thereof. The tool may be conveyed downhole on a wireline. Often times an evaluation tool is coupled to a tubular, such as a drill collar, and connected to a drill string used in drilling the borehole. Thus, evaluation and identification of formations and fluids can be achieved during drilling operations with measurement while drilling (MWD) or logging while drilling (LWD) tools. The several components and systems just described are suitable for various combinations as one of skill in the art would understand.
The downhole environment is rugged and dynamic, sometimes including high temperatures (e.g., above 175° C.), particularly while drilling. Survey instrumentation and sensors, such as magnetometers and accelerometers, can be sensitive to high temperatures. The high temperatures create errors in the sensors, sometimes called temperature drift. Thus, it is necessary to continually calibrate the magnetometers and accelerometers in the downhole survey instrument package to account for the constant temperature drift. The principles disclosed herein address the limitations of calibrating for temperature drift and other sensor errors in prior survey instrument packages.